Disposable hygiene articles are made from a wide variety of substrates (non-woven, elastomeric material, film, such as polyolefin film and in particular polyethylene or polypropylene film) bonded with adhesive materials. Among examples of disposable hygiene articles, mention may be made of diapers, napkins or adult incontinence disposable articles. The disposable hygiene articles are produced at high speed line rates.
In such production, hot melt adhesives are typically used because they can be easily applied to substrates (at the molten state) and rapidly develop strong bond upon cooling, without any additional manufacturing steps such as solvent removal.
Generally, several kinds of hot melt adhesives can be found in disposable hygiene articles, depending on their emplacement and final function, such as:                Core adhesives: used to keep in place the diaper core (fluff and SuperAbsorbentPolymer “SAP”), during the manufacture of the diaper but also during the use of the diaper mainly after that said diaper has been wet.        Construction adhesives: which bind the polyethylene back sheet to the nonwoven substrates or which bind two nonwoven substrates.        Elastic adhesives: used to bind elastic strands to polyethylene “PE” (or to polypropylene “PP”) and Nonwoven substrates.        
Styrenic bloc copolymers based adhesive are the main hot melt adhesives used in the absorbing articles industry (core, elastic and construction applications). Over the years, polyolefin based adhesives have been formulated, thanks to development of new polyolefins copolymers (Amorphous Poly-Alpha-Olefins “APAO” by Ziegler-Natta and then by Metallocene catalysis). However, the use of the polyolefin polymers was limited to construction adhesives, because of their poor processability (spraying), lack of cohesion and low creep resistance.
WO 2013/039262 describes a hot-melt adhesive composition comprising a propylene homopolymer and a wax modified with carboxylic acid and/or carboxylic acid anhydride. Said document does not describe the hot-melt adhesive composition of the invention.
In elastic attachment applications, adhesive is generally used to attach elastic material (such as polyurethane based strands) to sheet-like substrates. First, the elastic material is stretched prior to bonding and then adhesive is applied onto the elastics, either by spraying or contact applications, then the elastics coated with the adhesive are quickly laminated between a nonwoven substrate and a polyolefin film. After that, elastics are permitted to relax, creating a gathered (or rushed) laminate having substantial flexibility. The adhesive should maintain the elastics in place, particularly when solicited during manufacturing and use of the disposable hygiene article. This means that an adhesive with high cohesion and elasticity is required. In order to avoid any adhesive failure, good adhesion on the elastic strands is also recommended.
U.S. Pat. No. 6,329,468 describes the use of flexibile polyolefin FPO (based on propylene based polymers having a melt flow rate equal to or greater than 5 g/10 min and a density between 0.860 to 0.900 g/cm3. In U.S. Pat. No. 6,143,818, they also used a blend of ethylene-propylene copolymer and ethylene-propylene-diene monomer terpolymer and semi crystalline polymer. The disclosed hot melt adhesive composition shows good adhesion to a variety of substrates and good sprayability with high creep resistance. However, the application temperature is relatively high (175° C.-176° C.) which may limit the use of these adhesives especially in the case of thin and more sensitive substrates. Indeed, sensitive substrates may burn at high temperatures. Another drawback with the use of high temperatures is that they involve a higher energy consumption.
More recently, US 2010/0305528 describes polyolefins adhesive for elastic attachment applications comprising an ethylene/alpha-olefin copolymer and an acid anhydride modified polyolefin. US 2010/0305528 describes adhesive compositions with balanced properties of cohesive and adhesive strength. Said document has tested the creep resistance of the compositions with a high coating weight of adhesive composition.
Because of the insufficient elastic performances of polyolefin-based adhesive, commercially available elastic adhesives are today limited to styrene block copolymers based adhesive.
There is thus a need to develop adhesive compositions based on polyolefins for elastic attachments.